Page 224 - Reciprocating Compressors Operation Maintenance

Operation and Maintenance of Reciprocating Compressors 2O9

COMPRESSOR CYLINDER COOLING

BENEFITS OF CYLINDER JACKET COOLING

The major benefits of water cooling come from its role in reducing gas
temperature rise during compression. This is important. Gas discharge
temperature is a major factor in compressor maintenance.
High temperature results in:

1. Less effective lubrication
2. Deposits on valves
3. Shorter valve life
4. Higher cylinder maintenance costs
5. Increased risk of fires in discharge piping

Another benefit of lower gas temperatures is higher efficiency and
lower power requirements. Water-cooled units also can be designed for
higher single-stage pressures, that is, 125 vs. only 100 psig in air com-
pressors exceeding 100 horsepower. Additionally, water cooling main-
tains a more even temperature in the cylinder, thus reducing distortion.
Multistage compression with intercooling between stages permits con-
trol of the compression ratio and limitation of gas discharge temperature
to acceptable levels; for example, approximately one percent (1%) spe-
cific power saving for 10°F intercooling, based on air compressed to 100
psig in two stages.
More specifically, efficiency gains can be attributed to:

1. Dissipation of frictional heat generated by piston rings.
2. A flow of relatively cooler gas through the cylinder and jacket
cooling that prevents the temperatures of rubbing surfaces from ris-
ing too high.
3. Water jacketing that allows the existence of a high viscosity lubri-
cating oil film on the cylinder wall to reduce friction and wear.

It should be noted that whenever the cylinder is completely unloaded,
flow of fresh gas to carry the heat away is eliminated. Jacket cooling may
become essential in these circumstances.